1. Field of the Invention
The present invention relates to a display element which is provided with a display surface member having three or more odd display surfaces and is turned to select a desired one of the display surfaces. The invention also pertains to a display unit employing such display elements.
2. Description of the Prior Art
In Japanese Pat. Laid-Open No. 794995/87 there are disclosed a display element having four display surfaces and a display unit using such display elements.
The conventional display element has a display surface member with four display surfaces and a permanent magnet type motor mechanism. The display surface member is mounted on a rotor of the permanent magnet type motor mechanism housed therein and the four display surfaces are arranged side by side around the axis of the rotor.
The rotor of the permanent magnet type motor mechanism has first and second magnet members disposed side by side lengthwise thereof and each having north and south poles. The first and second magnet members are each a bar- or plate-like member of a narrow rectangular cross section in a direction perpendicular to the axis of the rotor and having the north and south poles at its both free end faces spaced an angular distance of 180 degrees apart around the axis of the rotor. The bar- or platelike member is mounted on the rotor shaft, with the center of the former in the above-mentioned cross section held in agreement with the center of the rotor axis. The north and south poles of the second magnet members are disposed around the axis of the rotor at an angular distance of plus or minus alpha degrees (where 0 degree is equal to or smaller than alpha degrees which is smaller than 180 degrees) from the north and south poles of the first magnet member.
Furthermore, the rotor of the permanent magnet type motor mechanism has a first magnetic member with first and second poles which act on the north and south poles of the first magnet member, a second magnet member with third and fourth poles which act on the north and south poles of the second magnet member, a first excitation winding wound on the first magnetic member in a manner to excite the first and second poles in opposite polarities, and a second excitation winding wound on the second magnetic member in a manner to excite the third and fourth poles in opposite polarities. The first and second poles of the first magnetic member are disposed at an angular distance of 180 degrees around the rotor axis. The third and fourth poles of the second magnetic member are disposed around the rotor axis at an angular distance of plus or minus 90 degrees plus or minus alpha degrees from the first and second poles of the first magnetic member. The first and second poles of the first magnetic member and the third and fourth poles of the second magnetic member respectively extend over an angular range of about 90 degrees around the rotor axis.
The display unit, disclosed in the afore-mentioned prior application, has the above-described display element and a drive unit therefor.
The drive unit has: first power supply means for supplying power to the first excitation winding of the display element to magnetize the first and second poles with the north and south magnetic poles; second power supply means for supplying power to the first excitation winding to magnetize the first and second poles with the north and south magnetic poles; third power supply means for supplying power to the second excitation winding of the display element to magnetize the third and fourth poles of the second magntic member with the north and south magnetic poles; and fourth power supply means for supplying power to the second excitation winding to magnetize the third and fourth poles with the south and north manetic poles.
With the disply element of the above-described construction, a selected one of the four display surfaces of the display surface member can be turned to the front display position by supplying power, in required polarity, to the first and second excitation windings of the rotor of the permanent magnet type motor mechanism.
Even if the power supply to the first and second excitation windings is cut off after turning the selected one of the four display surfaces to the front display position, it can be held there, because the first and second magnet is members of the rotor of the motor mechanism still act on the first and second magnetic members of the stator.
Moreover, since the permanent magnet type motor mechanism is housed in the display surface member, a display surface member driving mechanism need not be provided separaately of the display element.
In the display element disclosed in the afore-mentioned prior application and the display unit using it, it is necessary to supply power, in required polarities, to the first and second excitation windings of the motor mechanism to bring a desired one of the four display surfaces to the front display position-this presents some difficulty.
Besides, since the rotor of the permanent magnet type motor mechanism requires the first and second magnet members each having the north and south poles, the motor mechanism is inevitably complex and heavy, and the heavy rotor imposes a limitation on the high-speed operation of bringing a desired one of the four display surfaces to the front display position.